The present invention relates to a false twisting spindle of the fluid jet driving type. More particularly, the invention provides a false twisting spindle of the fluid jet driving type in which the rotation number of the spindle is at least 10,000,000 r.p.m.
An inventor has considered that if the rotation number is decided by the balance between the driving torque and the load torque, increase of the fluid jet pressure would result in increase of the rotation number. Based on this consideration, the fluid jet pressure had been increased and it was found that a maximum rotation number is obtained when the fluid jet pressure is a certain critical value and if the fluid jet pressure is increased beyond this critical value, the rotation number is lowered conversely, and that the value of the maximum rotation number varies depending on the diameter of the turbine blade and the value of the fluid pressure providing a maximum rotation number also varies depending on the diameter of the turbine blade. Standing on these finding, the present invention has been completed.